Tension device

ABSTRACT

A tension device with two preferably disc- or plate-shaped brake elements forced against one another by load devices and between which at least one thread to be braked can be led through. The brake elements are mounted on a bearing of a common bearing axle and capable of rotating freely about the bearing axle. The tension devise is provided with at least one magnetic loading device mounted on one of the two brake elements and at least one other magnetic loading device separate from the brake element with the magnetic loading device by which the brake elements are forced axially against one another.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a yarn brake with two preferably disc-shaped orplate-shaped brake elements pressed resiliently against one another bymagnetic loading.

2. Discussion of the Relevant Art

Yarn brakes of this type are used to a great extent for imparting yarntension to running yarns on textile machines and are known, for example,from EP 499 218 A2, DE-A 20 00 268, DE-C 864 073, GB-A 850,858 or DE 4301 507 A1.

These publications propose a yarn brake, in which the brake plates areinduced to clamp or brake the yarn by means of opposite-pole magneticrings. The braking force may be exerted in each case via a permanentlymagnetic ring which is arranged on the brake plate and which is fixedrelative to the brake plate via a thread. The forces of attraction ofopposite-pole permanent magnets depend on the distance between the twopermanently magnetic rings, there being an approximately square relationbetween the magnitude of the force of attraction and the distance. Thebraking force may thereby be set appropriately for the particularpurpose. However, the disadvantage of this arrangement and design ofbrake plates having opposite-pole magnetic rings is that it is notproperly possible to operate the yarn brake independently of position,and that sensitive adjustability of the braking force from zero up tothe full locking of the brake is made difficult.

Furthermore, the older application DE 44 09 450 A1 disclosed a genericyarn brake, in which additional axially polarized magnets are providedon the bearing shaft in order to assist the centring of the brakeplates. The magnets are polarized in such a way that they axially repellthe brake plate located in front of them in each case. At least one ofthe additional magnets is arranged axially adjustably on the bearingshaft.

The yarn brakes known from the prior art described above have in commonthe fact that relatively complicated solutions are provided in order toallow self-cleaning and, at the same time, sufficient fine adjustment ofthe braking force to achieve a high degree of operating reliability.

SUMMARY OF THE INVENTION

The object on which the invention, therefore, to provide a yarn brake ofthe type mentioned in the introduction, in which the rotatability of atleast one or of both brake plates for self-cleaning is achieved andmaintained in a simple and cost-effective way and sensitiveadjustability of the braking force and universal use in any installationposition and for different textile yarns in textile machines becomepossible.

A yarn brake comprising a first and a second disc- or plate-shaped brakeelements between which at least one yarn to be braked can be led througha first magnetic loading device, a second magnetic loading device thatis adjustable, a bearing shaft on which said first and second brakeelements are mounted to rotate freely about said bearing shaft, a stoparranged separately from said brake elements, a cover receiving saidsecond magnetic loading device arranged on said second brake element,and an adjusting unit.

The first and second brake elements are pressed in resiliently againstone another by the first and second magnetic loading devices. The firstmagnetic loading device is located on only one of the first and secondbrake elements. The second magnetic loading device is arrangedseparately from the first and second brake elements in such a way topress one of the first and second brake elements against the stop, andthe adjusting unit adjusts the force of the first and second magneticloading devices to adjust the press of the second brake element againstthe first brake element.

The separate or contactless arrangement of the loading elements makes itpossible to provide a yarn brake which has two brake elements pressedresiliently against one another by loading means and in which the brakeelements can be freely movable on the bearing shaft. At the same time,the brake plate provided with the loading means is pressed against theopposite brake plate which bears on a stop and which, on account of thehigher bearing friction, is consequently braked to a slightly greaterextent than the brake plate having the loading means. At least a minimaldifference in the circumferential speeds of the brake plates can bebrought about thereby. By virtue of these influences, which may occurboth individually and cumulatively, a high self-cleaning effect can beachieved.

By varying the distance between the two mutually repelling loadingmeans, the axial force of the brake elements can be adjusted, sincethere is a square relation between the magnitude of the force ofrepulsion and the distance.

This arrangement has, furthermore, the advantage that it can be usedirrespectively of the installation position. Furthermore, adjustabilityis provided over a larger range and while the yarn is running.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantageous developments of the yarn brake according to the inventionare described in the following detailed description. Preferredembodiments of the yarn brake according to the invention are explainedin more detail in the description of the Figures of which:

FIG. 1 shows a diagrammatic side view of a yarn brake according to theinvention with mutually repelling loading means,

FIG. 2 shows a diagrammatic side view of a yarn brake according to theinvention with mutually attracting loading means,

FIG. 3 shows a diagrammatic side view of the yarn brake according toFIG. 1 with a yarn guide slot, and

FIG. 4 shows a diagrammatic side view of a brake element together with aforce diagram of the forces transmitted to the brake elements via theyarn.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 illustrates a yarn brake 11 according to the invention. This hasa bearing shaft 12, of which the installation position, for example in ahorizontal orientation, is illustrated, but may be selectable asdesired. A first brake element 13 is mounted freely rotatably with playand a second brake element 14 is mounted freely rotatably on thisbearing shaft 12. The brake elements 13, 14 are of disc-shaped orplate-shaped design and have a central orifice 17, 18, the said orificesserving for mounting the brake elements 13, 14 on the bearing shaft 12.The brake elements 13, 14 are convexly curved in the manner of a torus,as seen in cross-section, and bear on one another in the region of theconvex curvature 16.

Bearing elements 19, 21 for the friction-reducing and/or wear-reducingreception of the brake elements 13, 14 on the bearing shaft 12 areprovided in the bearing orifices 17, 18 of the brake elements 13, 14.These bearing elements 19, 21 may be designed as bearing bushes orbearing rings. These bearing elements 19, 21 are advantageously producedfrom plastic which has good sliding properties along with high wearresistance.

In the bearing or effective region of the brake elements 13, 14, thebearing shaft 12 advantageously has a bearing sleeve 22 which isproduced from a hard and wear-resistant material, such as, for example,ceramic. This affords a high stability of the bearing shaft 12 withregard to the brake elements 13, 14 rotating freely on it and to a yarn23 which can be at least partially deflected around the bearing shaft12.

The bearing shaft 12 is received by the holder 26 which may be provided,for example, on a yarn delivery device (not illustrated). Provided tothe right of the holder 26, directly adjacent to the latter, is a stop27 which is advantageously produced from a wear-resistant plastic havinga low coefficient of friction. The first brake element 13 bears with itsbearing element 19 on this stop 27 and is limited to the left in itsaxial direction of movement and at least partially braked.

The second brake element 14 having a loading means 28 is illustratedopposite the first brake element 13. Illustrated at a distance from thissecond brake element 14 is a further loading means 29 which is receivedby an adjusting unit 31 and which is fixed relative to the bearing shaft12. In the exemplary embodiment, the loading means 28, 29 are designedas permanent magnetic rings which, in the embodiment shown in FIG. 1,have a like-pole arrangement, so that a repelling effect is achievedbetween the two magnets. An axial force of the second brake element 14is thereby achieved on the first brake element 13 which experiences acounterforce by means of the stop 27, with the result that the brakingforce is generated between the two brake elements 13, 14. The loadingmeans 28, 29 are arranged on the brake element 14 and the adjusting unit31 by means of an adhesive bond. Alternatively, the loading means 28, 29may be arranged non-positively and/or positively.

The adjusting unit 31 is designed as an adjusting nut which receives themagnetic ring 29. This adjusting nut can be adjusted continuously in theaxial direction on a thread 32 of the bearing shaft, so that fineadjustment of the braking force becomes possible. As regards thepermanent magnets, the relation applicable to the forces of attractionand repulsion is an approximately square relation between the magnitudeof the force of attraction and the distance. The axial force andtherefore the braking force between the brake elements 13, 14 can thusbe adjusted by a greater or lesser advance of the adjusting unit 31. Thethread 32 is advantageously designed as a self-locking thread, so thatslight displacement due to vibrations caused by the textile machinecannot occur. Alternatively, an adjusting unit 31 can be provided, whichis adjustable in steps and which can be set lockably by means ofpredetermined distances.

Furthermore, markings 33 may be provided on the bearing shaft 12, andthe said markings may be provided, for example, by means of worked-ingrooves or colour strips or the like, in order to allow the brakingforce of the brake elements 13, 14 to be preset. Furthermore, there maybe the possibility that, depending on the yarns to be processed, adifferent braking force is necessary, which can be set quickly by virtueof the markings 33, so that there can be fast resetting times.

The bearing shaft 12 is advantageously produced from non-magneticmaterial, so that a magnetic flux is ruled out between the loading means28, 29 and the bearing shaft 12. The force effect of the loading means28, 29 can be improved markedly thereby. It is perfectly possible,however, that the bearing shaft 12 can also be produced fromferromagnetic material, as stated below.

The brake elements 13, 14 are advantageously produced from ceramic oraluminium with a hard layer or preferably from non-magnetic steel.However, as already mentioned with regard to the design of the bearingshaft 12, there may be provision for producing the brake plates 13, 14from steel. There may also be provision for designing the brake element14 as a one-part magnetic component with the loading means 28 which,together with a non-magnetic brake element 13, forms part of the yarnbrake 11.

In order to prevent deposits of fluff, a cover 38 is advantageouslyprovided on the second brake element 14. This cover 38 is arrangedpositively and/or non-positively on the brake element 14. This cover 38may also fix the loading element 28 relative to the brake element 14,without a further connection- being necessary for this purpose. Thecover may be capable of being fastened to the brake element 14 by meansof a locking/snap or clamping connection. Alternatively, an adhesivebond may also be provided. The cover 38 is preferably designed as aninjection moulding. A cover 38 of this type may also be provided on theadjusting unit 31 and on the brake element 13.

In this exemplary embodiment, the bearing shaft 12 is received by aresiliently elastic holder 26, via which the natural oscillationfrequency of the textile machine can be transmitted to the bearing shaft12. It may thereby become possible, on the one hand, for deposits offluff to be shaken off. On the other hand, the oscillation frequency canbe transmitted to the brake elements 13, 14 and thus make it possiblefor the self-cleaning effect to be capable of being increased in asimple way. Alternatively, the bearing shaft 12 may be produced, atleast in portions, from resiliently elastic material, such as, forexample, plastic, and, in the case of a fixed holder 26, be capable ofbeing fastened relative to the holder 26 via an elastomeric bearing, inorder to utilize the oscillation of the textile machine.

The design according to the invention of a yarn brake 11 makes itpossible to have an arrangement independent of position and cantherefore be used for different yarns and textile filaments in differenttextile-processing machines.

FIG. 2 illustrates an alternative embodiment of the yarn brake 11according to the invention to that of FIG. 1. In this embodiment, theloading means 28, 29 are in an opposite-pole arrangement, so that theyhave an attracting effect. In order that a braking force can begenerated between the brake elements 13, 14, the first brake element 13once again bears on a stop 27 and is limited in the axial direction ofmovement to the left. By virtue of the attracting magnetic effect of theloading means 28, 29, the second brake element 14 is pressed with itsloading means 28 against the first brake element 13.

The thread 32, on which the adjusting unit 31 is arranged movably alongthe longitudinal shaft 12, is advantageously provided between the stop27 and the holder 26. Opposite the thread 32, the bearing shaft 12 has acollar 34, so that the brake elements 13, 14 are secured on both sidesin the axial direction. This collar 34 may directly adjoin the bearingsleeve 22. However, a minimum distance is necessary between the stop 27and the collar 34, so that the free rotatability of the brake elements13, 14 about the longitudinal shaft 12 is afforded, without thepossibility of friction impeding free rotatability.

Alternatively, there may be provision for arranging the holder 26between the adjusting unit 31 and the stop 27. The advantage of this isthat the yarn brake is arranged nearer to the holder 26. This isadvantageous particularly when already existing yarn delivery deviceshaving yarn brakes known from the prior art are retrofitted with theyarn brake according to the invention. As a result, an exchange of thebearing shaft 12 and at least of the second brake element 14 having theloading means 28 and of the additional arrangement of the adjusting unit31 having loading means 29 makes it possible to provide a yarn brake 11which does not require any change in the guidance of the yarn.

Apart from this the statements made with regard to FIG. 1 also apply.

FIG. 3 illustrates a development according to FIG. 1. The bearing shaft12 has a yarn guide slot 36 which runs essentially off-centre and whichextends until it reaches beyond the region of the lead 37 of the yarnthrough the yarn brake 11. It is thereby possible to ensure that theyarn can also be braked without being deflected, and escape from theyarn brake can be avoided. The yarn guide slot 36 may extend essentiallyaxis-parallel or at an oblique angle from a region laterally outside thebrake elements into the region of the yarn lead-through 37. Furthermore,bearing sleeves 22 may be provided, which have the yarn guide slot 36described above.

Alternatively to the yarn guide slot, two guide pins may also beprovided outside the yarn brake, the said guide pins being offset inparallel relative to the bearing shaft, so that the yarn bears reliablyon the bearing shaft and is guided.

FIG. 4 illustrates a diagrammatic side view of one of the brake elements13, 14 together with a yarn 23 which is deflected round a bearing sleeve22. Transmission of force from the yarn 23 to the brake element 13, 14takes place in the region of the convex curvature 16 of the brakeelement 13, 14. The resultant tensile force of the yarn 23 according tothe arrow 41 is composed of the force components in a tangential forceaccording to the arrow 42 and a radial force according to the arrow 43.At the entry and exit points of the yarn 23, it can be seen that thetangential forces according to the arrow 42 bring about a rotationalmovement in the direction of rotation according to the arrow 44. At thesame time, this rotational movement is braked as a result of a smallamount of sliding friction between the bearing elements 19, 21 of thebrake elements 13, 14 and the bearing element 19 and stop 27. This stateof equilibrium makes it possible, when the axial pressure changes andconsequently the braking force on the yarn 23 changes, for the drivetorque and the reaction torque of the mounting to change in the sameratio, so that an essentially constant slow rotational speed of thebrake elements 13, 14 is established and the self-cleaning effect isensured in any designed installation position.

Furthermore, there may alternatively be provision for the possibility ofproviding a plurality of first and second brake elements 13, 14 assignedto one another on a bearing shaft 12. In this case, it is merelynecessary that, for example in the case of both the repelling and theattracting arrangements, the brake element 14 furthest from the stop 27has a loading means 28.

A further improvement in the self-cleaning effect may be achieved by thebearing orifices 17, 18 of the brake elements 13, 14, the said bearingorifices surrounding the bearing shaft 12 with play, being designed soas to be eccentric by a small amount, with the result that it ispossible to achieve non-round running, by means of which yarn abrasioncan be removed even more effectively from the inner region between thebrake elements 13, 14.

There may be provision, furthermore, for the adjusting unit 31 to havemeans, via which motor-controlled adjustment becomes possible. This maybe carried out, for example, by using a long toothed belt which canengage on the adjusting unit or adjusting units 31 and can thus readjustone or more adjusting units 31 simultaneously.

A further advantage of the device according to the invention is to allowsimple exchangeability of a traditional yarn brake which consists, forexample, of two brake elements and of a compression spring with anadjusting nut which are arranged on a bearing shaft For this purpose, itis necessary to use at least one second brake element 14, with theloading means 28 arranged on it, and one adjusting unit 31 with loadingmeans 29. The first brake element 13 already present may continue to beused. An existing bearing shaft made of ferromagnetic material may, inprinciple, also continue to be used. In this case, however, it isnecessary, when a non-magnetic bearing shaft 12 is used, to set agreater advance of the adjusting unit 31 relative to the second brakeelement 14, in order to apply the same braking force, since a secondarymagnetic flux flows via the bearing shaft 12.

Advantageously, however, there is provision for installing the bearingshaft 12, the brake elements 13, 14 and the adjusting unit 31 on theholder 26 when the yarn brake is being exchanged.

The yarn brake according to the invention may equally be capable ofbeing used in the case of bobbin creels for beaming and warping systems,also known as beaming creels.

I claim:
 1. A yarn brake comprising:a first and a second disc- orplate-shaped brake element between which at least one yarn to be brakedcan be led through, a first magnetic loading device, a second magneticloading device that is arranged on said second brake element, a bearingshaft on which said first and second brake elements are mounted torotate freely about said bearing shaft, a stop arranged separately fromsaid first and second brake elements, an adjusting unit, and at leastone cover receiving said second magnetic loading device arranged on saidsecond brake element and said adjusting unit, in which: said first andsecond brake elements are pressed resiliently against one another bysaid first and second magnetic loading devices, said first magneticloading, device is arranged separately from said first and second brakeelements in such a way as to press one of said first and second brakeelements against said stop, and said adjusting unit adjusts the magneticeffect of said first and second magnetic loading devices to adjust thepress of said second brake element against said first brake element. 2.The yarn brake according to claim 1, in which:said first and secondmagnetic loading devices are located opposite each other and press saidfirst and second brake elements against one another by a repellingmagnetic effect of said first and second magnetic loading devices. 3.The yarn brake according to claim 1, in which:said first brake elementis arranged between said second brake element and said first magneticloading device so that said first and second brake elements are pressedagainst one another by magnetic attraction of said first and secondmagnetic loading devices.
 4. The yarn brake according to claim 1, inwhich said second brake element is made of non-magnetic material.
 5. Theyarn brake according to claim 1, in which said adjusting unit isarranged on said bearing shaft and can be adjusted continuously in theaxial direction of said bearing shaft.
 6. The yarn brake according toclaim 1, in which said adjusting unit comprises an adjusting nut.
 7. Theyarn brake according to claim 6, in which said adjusting nut is arrangedon a self-locking thread on said bearing shaft.
 8. The yarn brakeaccording to claim 1, in which said adjusting unit is displaceable onsaid bearing shaft at predetermined distances.
 9. The yarn brakeaccording to claim 1, in which at east one of said first and secondmagnetic loading devices comprises a magnetic ring.
 10. The yarn brakeaccording to claim 1, in which at least one of said first and secondmagnetic loading devices comprises at least one magnetic segment. 11.The yarn brake according to claim 1, in which said second magneticloading device is arranged positively or non-positively on said secondbrake element.
 12. The yarn brake according to claim 1, in which saidfirst magnetic loading device is arranged positively or non-positivelyon said adjusting unit.
 13. The yarn brake according to claim 1, inwhich said cover is made of plastic.
 14. The yarn brake according toclaim 1, in which said second brake element and said second magneticloading device comprise a replacement part that is arranged to bemounted interchangeably on said bearing shaft.
 15. The yarn brakeaccording to claim 1, in which said first magnetic loading device andsaid adjusting unit comprise a replacement part that is arranged to bemounted interchangeably on said bearing shaft.